1. Field of the Invention
The present invention relates to an optical transmitting and receiving module for coupling a light emitting device and a light receiving device with an optical fiber through which a plurality of transmitting light beams and receiving light beams having different wavelengths are transferred.
2. Description of the Related Art
There has been known an optical transmitting and receiving module which has a filter in order that a light beam with an unwanted wavelength is not incident on a receiving device, as that disclosed in Japanese Unexamined Patent Publication No. 8-160259. FIG. 6 shows a structure of such a conventional optical transmitting and receiving module. A light beam having a wavelength .lambda.1 emitted from a light emitting device 1 passes through an optical demultiplexing filter 2, is incident on an end face of an optical fiber 3, and is transmitted through the optical fiber 3. A light beam having a wavelength .lambda.2 received through the optical fiber 3 comes out from the end face of the optical fiber 3, is reflected from the optical demultiplexing filter 2, is collected by a lens 4, and is received by a light receiving device 6 through a filter 5. The filter 5 has a wavelength-selection feature in which a light beam having the wavelength .lambda.2 passes through the filter 5 and a light beam having a wavelength other than the wavelength .lambda.2 does not penetrate the filter 5.
Since the filter 5 for blocking a light beam having an unwanted wavelength from the light receiving device 6 is required for the above conventional optical transmitting and receiving module, however, the cost thereof is increased. In addition, because a space for placing the filter 5 is required, the module is prevented from being made compact.